High technology ceramics with partially stabilized zirconia

Abstract

A process for making a fully or a partially stabilized zirconia is disclosed. The process comprises making an aqueous solution of zirconium sulfate in admixture with an inorganic or organic water soluble salt of one or more metals selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ra, Sc, Y, La, Ac, Ce, Hf, Th and Al. The aqueous solution is atomized into a solvent at least partially miscible with water with the solvent being agitated during the addition of the solution. The coprecipitated metal salt formed is separated from the solvent, washed with inert solvent or solvents, dried, and calcined.

What is claimed is: 
     
       1. A process for making a fully or a partially stabilized zirconia comprising: (a) making an aqueous solution of zirconium sulfate in admixture with an inorganic or organic water soluble salt of one or more metals selected from the group consisting of Be, Mg, Ca, Sr, Ba, Ra, Sc, Y, La, Ac, Ce, Th, and Al, said organic salt having from about 1 to about 20 carbon atoms;   (b) atomizing said solution into a solvent at least partially miscible with water, said solvent present in an amount of at least 3 times the volume of said solution wherein the ratio of said solvent to said solution is about 3:1 to about 50:1, based on volume, said solvent being agitated during the addition of said solution, forming a coprecipitated metal salt;   (c) separating the coprecipitated metal salt from said solvent by filtration;   (d) washing the coprecipitated metal salt filtrate with an inert solvent or solvents;   (e) drying the washed filtrate; and   (f) calcining the dried filtrate in a flowing gas or mixture of gases.   
     
     
       2. A process of claim 1 wherein deionized, distilled, or millipore filtered water is used for said solution of (a) and wherein said coprecipitated metal salt is separated from said solvent by filtration. 
     
     
       3. A process of claim 1 wherein said solution of (a) is made by: (i) dissolving said zirconium sulfate in deionized, distilled or millipore filtered water to form a zirconium sulfate solution;   (ii) filtering said solution of (i) through a filter having pore sizes of about 0.2 to about 3 μm;   (iii) dissolving said organic or inorganic salt in deionized, distilled or millipore filtered water to form a salt solution;   (iv) filtering said solution of (iii) through a filter having pore sizes of about 0.2 to about 3 μm;   (v) mixing together said solutions of (ii) and (iv) to form said solution of (a).   
     
     
       4. A process of claim 1 wherein said solution of (a) has about 1 to about 2.5 moles/liter of zirconium sulfate and about 0.01 to about 0.5 moles/liter of said metal salt. 
     
     
       5. A process of claim 1 wherein said solution of (a) is filtered through a filter having a pore size of about 0.2 to about 3 μm before atomizing. 
     
     
       6. A process of claim 1 wherein said atomizing is by a pressure nozzle or ultrasonic nozzle. 
     
     
       7. A process of claim 1 wherein said solvent to solution ratio is about 5:1 to about 20:1. 
     
     
       8. A process of claim 1 wherein said solvent is agitated by mechanical stirring, magnetic stirring or by ultrasound. 
     
     
       9. A process of claim 1 wherein said solvent is selected from the group consisting of alcohols having from about 1 to about 8 carbon atoms and mixtures thereof, acetone, and tetrahydrofuran. 
     
     
       10. A process of claim 9 wherein said alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, n-butanol, isobutanol, and sec-butanol. 
     
     
       11. A process of claim 1 having the additional step of adding additional solvent to maintain water to solvent ratio of about 1:3 to about 1:50. 
     
     
       12. A process of claim 1 wherein said inert solvent of (d) is acetone. 
     
     
       13. A process of claim 1 wherein said inert solvent of (d) is acetone and toluene individually used sequentially with the first use of the sequence being acetone. 
     
     
       14. A process of claim 1 wherein said separated coprecipitated metal salt is dried at a temperature of about 120° C. 
     
     
       15. A process of claim 1 wherein said dried coprecipitated metal salt is calcined at a temperature of about 750° C. utilizing air as the flowing gas. 
     
     
       16. A process of claim 1 wherein said inorganic salt is selected from the group consisting of oxides, sulfates, chlorides, and nitrates; and said organic salt is selected from the group consisting of: citrates, formates, and acetates. 
     
     
       17. A process of claim 1 wherein (i) deionized, distilled, or millipore filtered water is utilized for said solution of (a);   (ii) said solution of (i) has about 1 to about 2.5 moles/liter of zirconium sulfate and about 0.01 to about 0.5 moles/liter of said metal salt;   (iii) said solution of (ii) is filtered through a   filter having pore sizes of about 0.2 to about 3 μm before atomizing;   (iv) said ratio of said solvent to said solution of (iii) is about 5:1 to about 20:1, said solvent being at least partially miscible with water, said solvent being agitated by mechanical stirring, magnetic stirring or ultrasound, said atomizing being by a pressure or a ultrasonic nozzle;   (v) additional solvent is added at a rate to maintain a water to solvent ratio of about 1:5 to about 1:20;   (vi) said separated coprecipitated salt is washed   with acetone;   (vii) said washed coprecipitated metal salt is dried at about 120° C. for about 1 to 2 hours; and   (viii) said dried coprecipitated metal salt is calcined at about 750° C. utilizing flowing air.   
     
     
       18. A process of claim 17 wherein the coprecipitated metal salt is separated by filtration. 
     
     
       19. A process of claim 17 wherein said solvent is selected from the group consisting of alcohols having from 1 to about 8 carbon atoms and mixtures thereof, chloroform, acetone, and tetrahydrofuran; and the metal salt is selected from the group consisting of oxides, sulfates, chlorides, formates, citrates, and acetates. 
     
     
       20. A process of claim 19 wherein said metal salt is selected from the group consisting of yttrium sulfates, calcium formates, calcium citrates, magnesium citrates, magnesium formates and magnesium sulfates. 
     
     
       21. A process of claim 19 wherein said metal salt is a yttrium sulfate and said solvent is ethanol. 
     
     
       22. A process of claim 19 wherein said metal salt is a yttrium sulfate and said solvent is methanol. 
     
     
       23. A process of claim 19 wherein said metal salt is a yttrium sulfate and said solvent is isopropanol. 
     
     
       24. A process of claim 19 wherein said metal salt is a yttrium sulfate and said solvent is selected from the group consisting of n-butanol and acetone. 
     
     
       25. A process of claim 19 wherein said metal salt is calcium formate and said solvent is isopropanol.